Use CHECK_CONDITION in Span::Sample() and Span::UnSample().
Use CHECK_CONDITION in Span::Sample() and Span::UnSample().

PiperOrigin-RevId: 437095470
Change-Id: I45292d3a52e4855063d733fb393d35acfd4e6032

google/tcmalloc,google/tcmalloc,google/tcmalloc